CN100570006C - The 20CrMnMo energy-saving carburizing composite heat treating process - Google Patents
The 20CrMnMo energy-saving carburizing composite heat treating process Download PDFInfo
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- CN100570006C CN100570006C CNB2008100369059A CN200810036905A CN100570006C CN 100570006 C CN100570006 C CN 100570006C CN B2008100369059 A CNB2008100369059 A CN B2008100369059A CN 200810036905 A CN200810036905 A CN 200810036905A CN 100570006 C CN100570006 C CN 100570006C
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Abstract
The present invention discloses a kind of 20CrMnMo energy-saving carburizing composite heat treating process, carries out according to the following step: one, carry out carburizing according to the suitable processing parameter of the workpiece choice of technology; Two, workpiece is slowly lowered the temperature with stove, and layer surface is progressively separated out a small amount of fine-structure mesh cementite, and when being cooled to 600-650 ℃, insulation for some time in the stove, workpiece generation austenite changes to the perlite recrystallization, the spheroidization of cementation zone carbide surface generation simultaneously; Three, be warming up to 820-840 ℃ of insulation, the quenching of coming out of the stove, making austenitic transformation is martensite; Four, carry out temper.This technology has greatly shortened the process time, enhances productivity, and improves hardness, wear resistance and the fatigue strength of workpiece.
Description
Technical field
The present invention relates to a kind of thermal treatment process, particularly the 20CrMnMo carburizing quenching process.
Background technology
Traditional carburizing and quenching mainly contains following several:
1. be cooled to quenching temperature after the carburizing, direct quenching after being incubated adopts this method to make material grains thick, and fragility is big, and the workpiece structural stress is big, can only be suitable for the less fine module gear of loading strength.
2. directly come out of the stove after the carburizing air cooling or the laggard burial pit of coming out of the stove is as cold as room temperature, advances the stove heating quenching again.Because the 20CrMnMo material behavior, carburizing postcooling speed is had strict demand, otherwise because during cooling, parts list layer tissue and time textura epidermoidea change non-synchronism, workpiece surface can produce bigger tensile stress, ftractures easily.The speed of cooling after the carburizing but is difficult to control.
3. the Deep Carburization Process part that specification of quality is high also can adopt the secondary quenching method, but so not only heat treatment stress is big in order to guarantee the quality index of surface cementation layer tissue and core structure simultaneously, and the danger of workpiece deformation cracking increases greatly.
4. as shown in Figure 1, stove is chilled to 550 ℃ after the 20CrMnMo carburizing, and the air cooling of coming out of the stove again is to room temperature, and advances stove again and be heated to 830-850 ℃ of insulation and quench tempering then.There are three shortcomings in such technology:
(1) it is low more favourable more to avoiding the workpiece surface oxidation and decarbonization to cool off temperature outward because of stove, but temperature is low more, cooling rate is slow more, cooling to 550 ℃ from 600 ℃ needed 8 hours approximately because the cool time of coming out of the stove is long, and intensification also needs the regular hour again, after stove is advanced in heating because workpiece quenches, will feed carburizing agent earlier and make process furnace reach certain carburizing atmosphere, in order to avoid workpiece surface decarburization when quenching heating influences work-ing life.Setting up needed carbon potential in stove also needs the regular hour, and traditional technology has long shortcoming of production cycle, and under present save energy, the environment that cuts down the consumption of energy, the market active demand can the comprehensive production cycle, the energy-saving and cost-reducing market requirement.
(2) production cycle long, reduced production efficiency.
(3) traditional Technology is that first stove is chilled to 550 ℃, and the air cooling of coming out of the stove again is to room temperature, and the scope that the back workpiece of coming out of the stove contacts with air increases, and workpiece surface is easy to oxidation and decarbonization.
In order to solve the problems of the technologies described above, be necessary a kind of new 20CrMnMo carburizing heat treatment process newly developed.
Summary of the invention
Technical problem to be solved by this invention is, and is long at the conventional 20CrMnMo carburizing heat treatment process cycle, energy consumption is high, easily oxidized shortcoming, a kind of 20CrMnMo carburizing composite heat treating process is provided, both shortened the process time, enhanced productivity, again energy efficient.
In order to solve the problems of the technologies described above, the present invention adopts following technical proposal:
As shown in Figure 2, a kind of 20CrMnMo energy-saving carburizing composite heat treating process, carry out according to the following step:
One, to workpiece carburizing under 920 ℃ of-940 ℃ of conditions, such as, can be 920 ℃, 925 ℃, 930 ℃, 930 ℃, 935 ℃ or 940 ℃.
Two, workpiece is slowly lowered the temperature with stove, and layer surface is progressively separated out a small amount of fine-structure mesh cementite, and when being cooled to 600-650 ℃, insulation for some time in the stove, workpiece generation austenite changes to the perlite recrystallization, the spheroidization of cementation zone carbide surface generation simultaneously; Deng the time and the workpiece size of thermophase, batch, case depth is relevant.Workpiece is big, and batch is big, and infiltration layer is dark, and isothermal time is answered proper extension.Nodularization effect in the thermophase carbide is also relevant with surface carbon content, if surface carbon concentration is higher, has formed coarse net or big massive carbide, and then nodularization effect is relatively poor.This also is the Control essentials of this carburizing combined heat treatment technology of speed reduction gear box.Selecting 600 ℃ of left and right sides isothermal temperatures, is in order to make the thick austenite crystal generation recrystallize phase transformation of carburizing.
Three, be warming up to 820-840 ℃ of insulation, the quenching of coming out of the stove, making austenitic transformation is martensite; Wherein, quench the heating phase, perlitic transformation becomes austenite, and the partially carbonized object depth of infiltration layer is gone into austenite, has guaranteed quench martensitic high rigidity in back and intensity.
Four, carry out temper.In the tempering stage, through 200 ℃ of-240 ℃ of stage tempering, quenched martensite is transformed into tempered martensite.Simultaneously, surperficial residual austenite is decomposed into martensite, has satisfied the technical qualification of gear surface high rigidity heart portion obdurability, has eliminated heat treatment stress.
Described tempering temperature is the arbitrary temperature in 200-240 ℃.
Feed carburizing agent in the described cementation process, such as, methyl alcohol or acetone.Can certainly be other carburizing agents.
Obvious technical effects of the present invention is embodied as:
After carburizing, need not the cooling of coming out of the stove, workpiece is still in the carbon potential atmosphere in stove, 20CrMnMo with depth of penetration 2.5-2.8mm is an example, the present invention shortened to 45 hours (disregarding tempering) with the process time of carburizing and quenching from original 68 hours, shorten the carburizing heat treatment process cycle 20%, it is about 10% to cut down the consumption of energy, and has also reduced the consumption of carburizing agent simultaneously, has opened up energy-efficient carburizing thermal treatment new way.
(2) thermal treatment process of the present invention's employing has reduced the link of coming out of the stove, and avoids workpiece to contact with air, thereby the surface oxidation decarburizing tendency reduces.
(3) isothermal process before the quenching has spheroidization to the cementation zone carbide surface after the carburizing, has increased the wear resistance of converted products, has improved the overall quality of product, increases substantially the work-ing life of processing parts.
(4) can guarantee carburized depth, hardness, the metallographic structure of 20CrMnMo, reduce the product tearing tendency, controllability is strong.
Description of drawings
Fig. 1 is conventional 20CrMnMo thermal treatment process synoptic diagram;
Fig. 2 is that the present invention is to 20CrMnMo thermal treatment process synoptic diagram;
Fig. 3 is that the present invention is to 20CrMnMo large gear thermal treatment process synoptic diagram;
Fig. 4 is that conventional thermal treatment process is to 20CrMnMo large gear thermal treatment process synoptic diagram.
Embodiment
In the present embodiment, be example with the 20CrMnMo large gear, effective working spaces size: diameter of phi 1700mm, high 1600mm, the Equipment for Heating Processing of employing is a pit gas carburizing furnace, batch: two in every stove, heating power: 180KW.Among Fig. 3, the modulus m=20 of large gear, size: Φ 1190mm * 330mm, single-piece weight: 1879kg, z=72.
As shown in Figure 3, operate according to the following step successively:
One, the 20CrMnMo large gear was heated 12 hours, reach 930 ℃, carburizing is 16 hours under 930 ℃ of conditions; The carburizing stage has been optimized the carbon potential that oozes, spreads each stage in the carburizing by force, and each processing parameter choose reasonable of time has reached depth of penetration, quality index such as nitrided layer hardness gradient with carburizing speed faster.
Two, with cold 7 hours to 600-620 ℃ of 20CrMnMo large gear stove, wherein, the cold stage of cementing furnace, slow reduction along with temperature, layer surface is progressively separated out a small amount of fine-structure mesh cementite, is as cold as≤austenite takes place 620 ℃ the time change to the perlite recrystallization, 600-620 ℃ of insulation 2 hours, make cementation zone carbide surface generation spheroidization, for preparation has been done in follow-up quenching.
Three, with 20CrMnMo large gear heating 2 hours to 830-840 ℃, be incubated 2 hours, the oil quenchinng of coming out of the stove, making austenitic transformation is martensite; Simultaneously, kept the not molten carbide particle of part in the austenite, after the quenching, workpiece surface is organized as fine acicular martensite and adds the carbide that a small amount of disperse distributes, and heart portion is lath martensite and a little ferrite.Gear has obtained surperficial high rigidity, high-wearing feature, high-fatigue strength, the use properties of the certain obdurability of heart portion.Novel process has significantly reduced the quenching technology holding time, is example with same batch (3T), and traditional technology rises to 840 ℃ from room temperature, and set up the carbon potential atmosphere need 10 hours, and novel process rises to 840 ℃ from 600 ℃ and only needs 3 hours, and carbon potential atmosphere need not to rebulid because of maintenance always in the stove.In addition, owing to be in all the time the protective atmosphere to the whole technological process workpiece that quenches from carburizing, after the thermal treatment, the gear surface oxidation and decarbonization is few, and the Heat Treatment Distortion amount is also less.
Four, carry out 2 hours temper.
In order to improve car-burization condition, feed carburizing agent methyl alcohol or acetone in the described cementation process.
The technical parameter that obtains after adopting thermal treatment process of the present invention that the 20CrMnMo large gear is handled is as follows:
Surface hardness: 60-61.5HRC
Effective case depth: CHD=4.82mm
Carbide surface rank: 2 grades
Surface martensite and residual austenite rank: 2 grades
Surface non-martensite microstructure 0.026mm
Core structure is a low carbon martensite, and heart portion ferrite rank is 2 grades.
Above-mentioned technical parameter meets following heat treatment technics requirement fully
Gear surface hardness: 58-62HRC
Centre hardness: 28-33HRC
Effective case depth: 4.3-4.9mm
Effective case depth: 2.5-4.9mm
Surface carbon content: 0.80-1.05%
Carbide surface rank: 1-3 level
Surface martensite and residual austenite rank: 1-4 level
Surface decarburization layer≤0.10mm
Outer martensitic stucture≤the 0.10mm in surface
Core structure: 1-4 level
Gear common normal size distortion franchise:＜1.0mm
Carburizing quality standard " JB/T 6141.2-92 heavy-duty gear carburizing quality test ".
As shown in Figure 4, adopt the time of conventional thermal treatment process to be:
The carburizing stage: heated 12 hours, and be incubated 16 hours, the air cooling 15 hours of coming out of the stove;
The quenching stage: heated 10 hours, and be incubated 2 hours, the oil cooling of coming out of the stove.
With regard to same 20CrMnMo large gear carburizing heat treatment, heat treatment of the present invention Technology is compared with conventional Technology for Heating Processing, can find out: (one) conventional Technology for Heating Processing Many 14 hours of time; (2) the present invention reduces the number of times of once coming out of the stove than conventional Technology for Heating Processing, Be conducive to energy savings, raise the efficiency, and avoid surface of the work oxidized.
Claims (4)
1. 20CrMnMo energy-saving carburizing composite heat treating process, carry out according to the following step:
One, to carrying out carburizing under 920 ℃ of-940 ℃ of conditions of workpiece;
Two, workpiece is slowly lowered the temperature with stove, and layer surface is progressively separated out a small amount of fine-structure mesh cementite, and when being cooled to 600-650 ℃, insulation for some time in the stove, workpiece generation austenite changes to the perlite recrystallization, the spheroidization of cementation zone carbide surface generation simultaneously;
Three, be warming up to 820-840 ℃ of insulation, the quenching of coming out of the stove, making austenitic transformation is martensite;
Four, carry out temper.
2. 20CrMnMo energy-saving carburizing composite heat treating process according to claim 1 is characterized in that: described tempering temperature is 200-240 ℃.
3. 20CrMnMo energy-saving carburizing composite heat treating process according to claim 1 and 2 is characterized in that: feed carburizing agent in the described cementation process.
4. 20CrMnMo energy-saving carburizing composite heat treating process according to claim 3 is characterized in that: described carburizing agent is methyl alcohol or acetone.
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Cited By (1)
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| CN106555153A (en) * | 2015-09-29 | 2017-04-05 | 常州兰翔机械有限责任公司 | A kind of blade mounting seat heat treatment method |
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| CN102392260A (en) * | 2011-10-11 | 2012-03-28 | 天津市祥威传动设备有限公司 | Carburizing direct quenching process for large-scale wind power gear/gear shaft |
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| CN102703909A (en) * | 2012-05-24 | 2012-10-03 | 浙江吉利汽车研究院有限公司杭州分公司 | Combined carburizing and quenching process for improving gear performance |
| CN103290419B (en) * | 2013-06-25 | 2015-04-15 | 清华大学 | Gear treatment method |
| CN103468916A (en) * | 2013-07-29 | 2013-12-25 | 江阴市科安传动机械有限公司 | Heat treatment process for bevel gear |
| CN103643200A (en) * | 2013-11-26 | 2014-03-19 | 常熟市东风齿轮厂 | Composite carburization quenching technology for gear |
| CN104451043A (en) * | 2014-11-29 | 2015-03-25 | 江西洪都航空工业集团有限责任公司 | Intensive quenching process for 20CrMnMo steel |
| CN104531970A (en) * | 2015-01-22 | 2015-04-22 | 蚌埠市钰诚五金工贸有限公司 | Carburizing and quenching process for composite wallboard tapping screws |
| CN104726819B (en) * | 2015-03-20 | 2017-09-19 | 上海人本集团有限公司 | Carburizing Heat-Treatment of Steel carburization process |
| CN107299204A (en) * | 2017-03-31 | 2017-10-27 | 西南大学 | A kind of processing method of raising 20CrMnMo hardness of steel |
| CN108823501A (en) * | 2018-08-07 | 2018-11-16 | 湖北威能达传动有限责任公司 | A kind of heat treatment process of 20CrMnMoA steel pricker gear shaft |
| CN108866311A (en) * | 2018-08-07 | 2018-11-23 | 湖北威能达传动有限责任公司 | A kind of heat treatment process of 20CrMnMoA steel pricker gear |
| CN109182719B (en) * | 2018-10-26 | 2020-09-04 | 厦门真冈热处理有限公司 | Heat treatment method for pinion of automobile electric steering system |
| CN115109899A (en) * | 2022-06-27 | 2022-09-27 | 北京机电研究所有限公司 | Heat treatment process of low-carbon alloy steel material |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106555153A (en) * | 2015-09-29 | 2017-04-05 | 常州兰翔机械有限责任公司 | A kind of blade mounting seat heat treatment method |
| CN106555153B (en) * | 2015-09-29 | 2018-09-21 | 中国航发常州兰翔机械有限责任公司 | A kind of blade mounting base heat treatment method |
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Application publication date: 20080917 Assignee: Shanghai Longqian Heat Treatment Co., Ltd. Assignor: Shanghai Heat Treatment Co., Ltd. Contract record no.: 2011310000069 Denomination of invention: 20CrMnMo energy-saving carburizing composite heat treating process Granted publication date: 20091216 License type: Exclusive License Record date: 20110526 |
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